Fermentation by fungi converts stored pollen into bee bread
that is fed to honey bee larvae, Apis mellifera, so the diversity of fungi in
bee bread may be related to its food value. To explore the relationship between
fungicide exposure and bee bread fungi, samples of bee bread collected from bee
colonies pollinating orchards from 7 locations over 2 years were analyzed for
fungicide residues and fungus composition.

There were detectable levels of fungicides from regions that
were sprayed before bloom. An organic orchard had the highest quantity and
variety of fungicides, likely due to the presence of treated orchards within
bees' flight range. Aspergillus, Penicillium, Rhizopus, and Cladosporium
(beneficial fungi) were the primary fungal isolates found, regardless of
habitat differences. There was some variation in fungal components amongst colonies,
even within the same apiary. The variable components were Absidia, Alternaria,
Aureobasidium, Bipolaris, Fusarium, Geotrichum, Mucor, Nigrospora,
Paecilomyces, Scopulariopsis, and Trichoderma. The number of fungal isolates
was reduced as an effect of fungicide contamination. Aspergillus abundance was
particularly affected by increased fungicide levels, as indicated by Simpson's
diversity index.